import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: HP
 * Date: 2023 -04 -26
 * Time: 22:27
 */
public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;
        return A;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root==null) return;
        System.out.print(root.val+ " ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root==null) return;
        inOrder(root.left);
        System.out.print(root.val+ " ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root==null) return;
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+ " ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    int size(TreeNode root) {
        if(root==null) return nodeSize;
        nodeSize++;
        size(root.left);
        size(root.right);
        return nodeSize;
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if(root==null) return 0;
        return size2(root.left)+size2((root.right))+1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    int getLeafNodeCount1(TreeNode root) {
        if(root==null) return leafSize;
        if(root.left==null&&root.right==null){
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
        return leafSize;
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if(root==null) return 0;
        if(root.left==null&&root.right==null) return 1;
        return getLeafNodeCount2(root.left)+getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if(root==null) return 0;
        k--;
        if(k==0) return 1;
        return getKLevelNodeCount(root.left,k)+getKLevelNodeCount(root.right,k);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if(root==null) return 0;
        return Math.max(getHeight(root.left),getHeight(root.right))+1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if(root==null) return null;
        if(root.val==val) return root;
        TreeNode left=find(root.left,val);
        if(left!=null) return left;
        return find(root.right,val);
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if(root==null) return;
        Queue<TreeNode> q=new LinkedList<>();
        q.offer(root);
        while(!q.isEmpty()) {
            TreeNode front = q.poll();
            System.out.print(front.val + " ");
            if (front.left != null) q.offer(front.left);
            if (front.right != null) q.offer(front.right);
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if(root==null) return true;
        Queue<TreeNode> q=new LinkedList<>();
        q.offer(root);
        while(!q.isEmpty())
        {
            TreeNode top=q.poll();
            if(top!=null) {
                q.offer(top.left);
                q.offer(top.right);
            }
            else{
                break;
            }
        }
        while(!q.isEmpty())
        {
            TreeNode top=q.poll();
            if(top!=null) return false;
        }
        return true;
    }

    public static void main(String[] args) {
        BinaryTree binaryTree = new BinaryTree();
        BinaryTree.TreeNode root = binaryTree.createTree();
        binaryTree.preOrder(root);
        System.out.println();
        //非递归实现！
//        binaryTree.preOrderNor(root);
//        System.out.println();
        System.out.println("=======================");

        binaryTree.inOrder(root);
        System.out.println();
//        binaryTree.inOrderNor(root);
//        System.out.println();
        System.out.println("============上面是中序遍历===========");

        binaryTree.postOrder(root);
        System.out.println();
//        binaryTree.postOrderNor(root);
//        System.out.println();
        System.out.println("============上面是后序遍历===========");


        System.out.println("节点的个数: ");
        System.out.println(binaryTree.size(root));
        System.out.println(binaryTree.size2(root));
        System.out.println("叶子节点的个数：");
        System.out.println(binaryTree.getLeafNodeCount1(root));
        System.out.println(binaryTree.getLeafNodeCount2(root));
        System.out.println("======第K层的节点个数========");
        System.out.println(binaryTree.getKLevelNodeCount(root, 4));
        System.out.println("======树的高度========");
        System.out.println(binaryTree.getHeight(root));
        System.out.println("======查找========");
        BinaryTree.TreeNode ret = binaryTree.find(root,'E');
        System.out.println(ret.val);
        System.out.println("层序遍历：");
        binaryTree.levelOrder(root);
        System.out.println();
        System.out.println("是否是完全二叉树：");
        System.out.println(binaryTree.isCompleteTree(root));
    }
}